1. Field of the Invention
The present invention relates to a liquid jet recording head used for a liquid jet recording apparatus of a bubble jet type or the like which discharges recording liquid (ink) from orifices (discharge ports) as droplets. The invention also relates to a method of manufacture for such head, and a liquid jet recording apparatus upon which is mounted a liquid jet recording head manufactured by such method.
2. Related Background Art
A liquid jet recording apparatus of a bubble jet type or the like is insensitive to external disturbances, and provides a good rate of recording. Therefore, such an apparatus is suited to performing high-speed printing with good precision, and in colors, among its other advantages. The future of this type of apparatus is promising. As shown in FIGS. 13A and 13B, a liquid jet recording head used for a liquid jet recording apparatus of the kind is provided with a base board 1001 having discharge energy generating elements, and a nozzle layer (liquid path formation layer) 1002 that forms liquid paths 1002b conductively connected to orifices (discharge ports) 1002a and a liquid chamber. Generally, there are formed on the base board 1001 discharge energy generating elements 1011 by the known technique of photo-lithography after an SiO.sub.2 thermal oxidation film 1001a is provided on a monocrystal Si substrate. The surface thereof is covered by an electric insulation layer of SiO.sub.2, SiC, Si.sub.3 N.sub.4, or the like, and also, by a protection layer 1001b formed by Ta film or the like for the prevention of damage (such as cavitation erosion) that would otherwise be caused to the discharge energy generating elements due to mechanical shocks occurring when recording liquid is discharged. Here, if necessary, a film of Ta.sub.2 O.sub.5, or the like is provided between the electric insulation layer and the Ta film in order to strengthen the contact between them. Also, on the nozzle layer 1002, a glass ceiling plate 1003 and others are arranged with an injection inlet to supply ink or other recording liquid.
A liquid jet recording head of this kind is generally manufactured by the steps of:
coating a photoresist on the base board having discharge energy generating elements on it; PA1 providing a resist pattern having an inverted shape of the nozzle layer by causing the board thus coated to be exposed and developed; PA1 covering the board thus prepared with the glass ceiling plate, and then, injecting molten resin into the space on the circumference of the resist pattern; PA1 hardening the resin and forming the orifice surface by cutting the workpiece along a predetermined cutting face; and lastly, PA1 eluting the resist pattern by use of a solution to form each of the liquid paths on the nozzle layer.
In place of the injection molding method described above, there is another method for forming the nozzle layer wherein a photohardening resin is coated on the base board having a resist pattern on it, and then, after the glass ceiling plate is installed on it, a beam is irradiated from above it to harden the resin. In this case, too, such steps are needed that after the resin is hardened, the workpiece is cut along a predetermined face, and that the resist pattern is eluted.
In order to enhance the production of the liquid jet recording heads, a method is adopted in which when the head is manufactured the nozzle layers are laminated for a portion of plural liquid jet recording heads on a base board having a large area, such as a six-inch or an eight-inch wafer as in the case of a semiconductor process, and then, the laminated body is cut cut up using a cutting blade to form the individual liquid jet recording heads, and that the cutting faces which define the orifice surfaces are ground and polished for finishing.
However, in accordance with the conventional techniques described above, the nozzle layers are laminated on a large base board for a portion of plural liquid jet recording heads, and the laminated body thus obtained is cut up into each of the liquid jet recording heads. This cutting process is performed using a cutting blade adopted from a usual semiconductor process, which has a cutting width of several tens of .mu.m to one mm. Therefore, as shown in FIG. 14, it is impossible to avoid creating a chipped portion V.sub.1 on the base board 1001 with respect to the cutting face of the liquid jet recording head, which is an orifice surface, a chipped portion V.sub.2 on the nozzle layer 1002, or a crack V.sub.3 on the nozzle layer 1002.
Compared with the chipped portion V.sub.2 and the crack V.sub.3 on the nozzle layer 1002, the chipped portion V.sub.1 on the base board, in particular, tends to adversely effect to a considerable extent the shapes of the discharge ports 1002a and liquid paths 1002b on the nozzle layer 1002. For example, if an Si substrate of 0.5 mm or more in thickness is used for the basic material for the base board 1001, the discharging direction of ink is conspicuously changed, thus resulting in twisted printing, as well as other defects, because the depth of the chipped portion V.sub.1 of the base board 1001 may be as much as 10 .mu.m or more.
This is due to the fact that the basic material from which the base board is formed is a Si substrate, which is hard and brittle, and the heat accumulation layer, protection layer, and others provided on it are also formed mainly from SiO.sub.2, which is equally hard and brittle. As a result, the base board has properties as whole making it extremely likely to be chipped off or otherwise damaged.